<template lang="html">
  <scroll class="listview" :data="data"
  ref="listview"
  :listenScroll="listenScroll"
  @scroll="scroll"
  :probeType="probeType">
    <ul>
      <!-- list-view 的原因是L和V大写 -->
      <li v-for="group in data" class="list-group" ref="listGroup">
        <h2 class="list-group-title">{{group.title}}</h2>
        <ul>
          <li v-for="item in group.items" class="list-group-item">
            <img class="avatar" v-lazy="item.avatar">
            <span class="name">{{item.name}}</span>
          </li>
        </ul>
      </li>
    </ul>
    <div class="list-shortcut" @touchstart="onShortcutTouchStart" @touchmove.stop.prevent="onShortcutTouchMove">
      <ul>
        <li v-for="(item,index) in shortcutList" class="item"
        :class="{'current':currentIndex==index}"
        :data-index="index">
          {{item}}
        </li>
      </ul>
    </div>
  </scroll>

</template>

<script>
import Scroll from 'base/scroll/scroll'
import {
  getData
} from 'common/js/dom'
const ANCHOR_HEIGHT = 18

export default {
  created() {
    this.touch = {}
    this.listenScroll = true
    this.listHight = []
    this.probeType = 3
  },
  props: {
    data: {
      type: Array,
      default: []
    }
  },
  data() {
    return {
      scrollY: -1,
      currentIndex: 0
    }
  },
  computed: {
    shortcutList() {
      return this.data.map((group) => {
        return group.title.substr(0, 1)
      })
    }
  },
  methods: {
    //私有方法放下面，绑定事件的放上面
    scroll(pos) {
      this.scrollY = pos.y

    },
    onShortcutTouchStart(e) {
      console.log("start");
      let anchorIndex = getData(e.target, 'index')
      let firstTouch = e.touches[0]
      this.touch.y1 = firstTouch.pageY
      this.touch.anchorIndex = anchorIndex

      this._scrollTo(anchorIndex)

    },
    onShortcutTouchMove(e) {
      console.log("move");
      let firstTouch = e.touches[0]
      this.touch.y2 = firstTouch.pageY
      // | 0 为向下取整
      let delta = (this.touch.y2 - this.touch.y1) / ANCHOR_HEIGHT | 0
      let anchorIndex = parseInt(this.touch.anchorIndex) + delta
      this._scrollTo(anchorIndex)

    },
    _scrollTo(index) {
      this.$refs.listview.scrollToElement(this.$refs.listGroup[index], 0)
    },
    _calculateHeight() {
      this.listHight = []
      const list = this.$refs.listGroup
      let height = 0
      this.listHight.push(height)
      for (let i = 0; i < list.length; i++) {
        let item = list[i]
        height += item.clientHeight
        this.listHight.push(height)

      }

    }
  },
  watch: {
    data() {
      setTimeout(() => {
        this._calculateHeight()
      }, 20);
    },
    scrollY(newY) {
      const listHeight = this.listHight
      for (let i = 0; i < listHeight.length; i++) {
        let heightl = listHeight[i]
        let height2 = listHeight[i + 1]
        if (!height2 || (-newY > heightl && -newY < height2)) {
            this.currentIndex = i
            return
          }
        }
        this.currentIndex = 0
      }
    },
    components: {
      Scroll
    }
  }
</script>

<style scoped lang="stylus" rel="stylesheet/stylus">
  @import "~common/stylus/variable"

  .listview
    position: relative
    width: 100%
    height: 100%
    overflow: hidden
    background: $color-background
    .list-group
      padding-bottom: 30px
      .list-group-title
        height: 30px
        line-height: 30px
        padding-left: 20px
        font-size: $font-size-small
        color: $color-text-l
        background: $color-highlight-background
      .list-group-item
        display: flex
        align-items: center
        padding: 20px 0 0 30px
        .avatar
          width: 50px
          height: 50px
          border-radius: 50%
        .name
          margin-left: 20px
          color: $color-text-l
          font-size: $font-size-medium
    .list-shortcut
      position: absolute
      z-index: 30
      right: 0
      top: 50%
      transform: translateY(-50%)
      width: 20px
      padding: 20px 0
      border-radius: 10px
      text-align: center
      background: $color-background-d
      font-family: Helvetica
      .item
        padding: 3px
        line-height: 1
        color: $color-text-l
        font-size: $font-size-small
        &.current
          color: $color-theme
    .list-fixed
      position: absolute
      top: 0
      left: 0
      width: 100%
      .fixed-title
        height: 30px
        line-height: 30px
        padding-left: 20px
        font-size: $font-size-small
        color: $color-text-l
        background: $color-highlight-background
    .loading-container
      position: absolute
      width: 100%
      top: 50%
      transform: translateY(-50%)
</style>
